In attempts to prepare injection molded, thin-walled parts from carbonate polymer resins, it has been observed that such articles prepared from carbonate polymer resins are affected by the molecular weight (Mw). It is known that the processability of carbonate polymer resins decreases as the molecular weight of the carbonate polymer resins increases, the higher molecular weight resins being more difficult to process due to their higher viscosity and corresponding lower melt flow rate.
For example, in Japanese Patent Publication 03-243,655 (1992) amounts of a lower molecular weight carbonate polymer are incorporated into a high molecular carbonate polymer composition in attempting to improve the flow and processability properties of such carbonate polymers. However, it is known that higher and lower molecular weight components are often difficult to homogeneously blend due to their differences in melt viscosities and do not produce the best possible combinations of polymer processability and molded part physical properties.
In Japanese Patent Publication 60-215,051 (1985) it is shown that branched resins can be incorporated in varying amounts into blends with a higher melt flow rate, low molecular weight linear carbonate polymer to improve the melt strength of the low molecular weight resin. In U.S. Pat. No. 3,931,108 certain branched resins are shown to be extrudable into film with improved stress crack resistance. In U.S. Pat. No. 4,912,194 it is proposed that crosslinked or branched polycarbonates can be prepared by incorporating a diester diphenolic monomer into the carbonate polymer backbone, then heat activating the crosslinking reaction. In U.S. Pat. No. 3,770,697 and U.S. Pat. No. 3,652,715 carbonate polymers are provided with thermally activated, terminal or pendant unsaturated imido groups which can be reacted. Branched resins, however, have been found to have somewhat lower impact resistance values than a corresponding linear resin of the same melt flow rate.
It is therefore a goal of the present invention to provide an improved easy flow carbonate polymer resin, an improved process for the preparation of injection molded, thin-walled corner parts and improved injection molded, thin-walled corner parts themselves.